Sphinx of black quartz, judge my vow

[ihcoyc]

The interpretation of English spelling by fluent speakers is an amazingly complicated phenomenon. All readers of English are amateur etymologists predicting the contemporary spoken outcome of an ancient root form, where the evidence of the ancient root is the written string of letters. Confronted with the string, it's assigned a level of exoticism, in ascending order:

Core Germanic English (go, want, have)
Anglo-Norman French (flour, display)
More recent French (lingerie, ennui)
Greco-Latin learned vocabulary (pneumatic, rhinoceros)
Exotic odd lots (pizza, ukelele)

The classification determines which rule set must be applied to produce a spoken form from writing.

The first two are almost equally basic, but there are distinguishing pairs showing the existence of two rule sets: gilt vs. gist, for example. There are clues, of course: the presence of odd combinations in the syllable onset like "phth-" or "pn-" pretty much forces a written word into the learned rule set. But nothing much distinguishes an early borrowed French word like devour from a more recent French word like velour.

Any one of the rule sets could be applied consistently: when the system breaks down, it's almost always the result of faulty assignment.